Visible light-induced electronic structure modulation of Nb- and Ta-doped α-Fe2O3 nanorods for effective photoelectrochemical water splitting.

The photoelectrochemical (PEC) water splitting activity of Nb and Ta-doped hematite (α-Fe2O3) nanorods was investigated with reference to electronic structures by in situ synchrotron x-ray absorption spectroscopy (XAS). Current density-potential measurements demonstrate that the PEC activity of α-Fe2O3 nanorods depends strongly on the species and concentrations of dopants. The doping of α-Fe2O3 nanorods with a low level of Nb or Ta can improve their electrical conductivity and thereby facilitate charge transport and reduced electron-hole recombination therein. The photoconversion effects of Nb and Ta-doped α-Fe2O3 by in situ XAS in the dark and under illumination revealed opposite evolutions of the spectral intensities of the Fe L-edge and Nb/Ta L-edge, indicating that charge transfer and a conduction pathway are involved in the photoconversion. Analytic in situ XAS results reveal that the α-Fe2O3 that is doped with a low level of Nb has a greater photoconversion efficiency than that doped with Ta because Nb sites are more active than Ta sites in α-Fe2O3. The correlation between PEC activity and the electronic structure of Nb/Ta-doped α-Fe2O3 is examined in detail using in situ XAS and helps to elucidate the mechanism of PEC water splitting in terms of the electronic structure.

Operando X-ray spectroscopic observations of modulations of local atomic and electronic structures of color switching smart film.

Smart windows, which change color in response to external stimuli, are extensively studied owing to their potential technological applications in sensors and their ability to reduce the energy consumed by buildings. Most related studies focus on the optical properties of smart color switching films that can control the transmission of light and that of heat independently. This study examines the vanadium pentoxide thin film as a model system of a color switchable window. A gasochromic thin film of V2O5 is fabricated using sol-gel spin coating. In operando soft X-ray absorption spectroscopy (XAS) at the V L-edge is used to determine the evolutions of the electronic and atomic structures of V2O5 thin film under gasochromic color switching. Analysis of the V K-edge with respect to crystalline structural symmetry and valence requires many reference samples, whereas the V L-edge, which involves V 3d orbitals of various symmetries, can provide information about the atomic/electronic structures without many reference samples. A new gas reaction in situ cell was developed to collect the total-electron-yield XAS. The total-electron-yield signal can provide more accurate information about atomic and electronic structures than can the fluorescence-yield signal, which typically exerts a saturation effect. Analytical results reveal that the gasochromic reaction changes the charge state and causes a local atomic structural deformation of the film. The suggestion has been made that in the reaction, the central vanadium atom within the octahedron moves closer to the basal plane such that the apical V-O bond becomes more symmetrical than the film before gasochromic coloration. Unlike the cell that is used for hard XAS, and for which only cation sites can be studied, this in situ gas cell enables the real-time studies of atomic/electronic structures at gas-solid interfaces from viewpoints of both cation and anion sites.

Atomic and electronic aspects of the coloration mechanism of gasochromic Pt/Mo-modified V2O5 smart films: an in situ X-ray spectroscopic study.

In this work, gasochromic pristine and Mo-modified V2O5 thin films were prepared by the sol-gel spin coating method. Both films exhibit excellent gasochromic coloration. Synchrotron grazing incidence X-ray diffraction reveals that the Mo-modified V2O5 thin film is more amorphous than the pristine V2O5 thin film. X-ray absorption spectroscopy (XAS) was utilized to elucidate the modifications of the local electronic and atomic structures that are caused by Mo. In situ soft-XAS and in situ hard-XAS were performed to monitor the effect of the adsorption of dihydrogen on the charge state of vanadium and local atomic rearrangement in the gasochromic thin films. The gasochromic V2O5 film has a significantly pyramid-like oxygen-coordinated environment. However, the Mo-modified film exhibits mixed pyramid- and octahedral-like structures. Analytic results indicate that upon gasochromic coloration, adsorption of hydrogen adds electrons to the V 3d t2g orbital, lowering the charge state of vanadium. The films undergo structural modification before the valence is changed. The Mo-modified V2O5 film exhibits faster coloration because the apical V-O bond differs from that in the pristine V2O5 film. This in situ XAS allows real-time monitoring of changes in the element-specific local atomic structure during the gasochromic reaction and enables the elucidation of the gasochromic mechanism.

Electrochemical and in situ X-ray spectroscopic studies of MnO2/reduced graphene oxide nanocomposites as a supercapacitor.

Electrochemical and in situ X-ray absorption spectroscopy (XAS) measurements of various MnO2-coated carbon materials (MnO2/acid-functionalized carbon nanotubes (C-CNT), MnO2/reduced graphene oxide (RGO), and MnO2/RGO-Au electrodes) were conducted to evaluate the supercapacitive performances and electronic structures. MnO2 was deposited on the surface of C-CNT, RGO, and RGO-Au via a spontaneous redox reaction to facilitate the growth of the bulk form of MnO2/C-CNT and the surface forms of MnO2/RGO-based materials. Various forms of MnO2 on the carbon materials exhibited different charge/discharge behaviors. The specific capacitances of the MnO2/RGO and MnO2/RGO-Au electrodes at a current density of 1 A g(-1) were about 433 and 469 F g(-1), respectively; these values are about 1.5 times that of the MnO2/C-CNT (259 F g(-1)) electrode. Specific capacitances of 220 and 281 F g(-1) with retention rates of about 50-60% were obtained from MnO2/RGO and MnO2/RGO-Au, respectively, even at a high current density of 80 A g(-1). Experimental results revealed that the long-term electrochemical stability of the MnO2/RGO-based electrodes (with ∼90% retention) exceeded that of the MnO2/C-CNT electrode (with ∼60% retention) after 1000 cycles at a high scan rate of 80 A g(-1). This finding indicates that MnO2/RGO-based electrodes feature excellent cycling stability and rate capacity retention performance. To elucidate the atomic/electronic structures of the MnO2/C-CNT, MnO2/RGO, and MnO2/RGO-Au electrodes during the charge/discharge process, in situ XAS of the Mn K-edge was performed. The MnO2/RGO-based electrodes exhibited the least variations in the pre-peak intensity of the Mn K-edge during the charge/discharge process because a nano-network of MnO2 is homogeneously decorated on the outer surfaces of RGO-based electrodes to facilitate the growth of surface forms of MnO2/RGO and MnO2/RGO-Au. Analytical results further revealed suppression of changes in tunnel size and promotion of insertion/extraction behavior. This work, particularly the combination of cyclic voltammetry with in situ XAS measurements, will be of general value in the fields of nanomaterials and nanotechnology, and in their use in energy storage.

Simulating far infrared spectra of Zn1-xMnxSe/GaAs epifilms, MnSe/ZnSe superlattices and predicting impurity modes of N, P defects in Zn1-xMnxSe.

A comprehensive lattice dynamical study is reported to emphasize the vibrational behavior of perfect/imperfect zinc-blende (zb) ZnSe, MnSe and Zn1-xMnxSe alloys. Low temperature far-infrared (FIR) reflectivity measurements performed on a series of molecular beam epitaxy grown Zn1-xMnxSe/GaAs (001) epilayers have a typical 'intermediate-phonon-mode' behavior. Besides perceiving ZnSe- and MnSe-like TO-phonon resonances, the study also revealed a weak Mn alloy-disorder mode below MnSe band. A classical effective-medium theory of multilayer optics is used to evaluate dielectric tensors of both epilayers and substrate for simulating reflectivity and transmission spectra of ultrathin epifilms and superlattices at near normal and/or oblique incidence. In the framework of a realistic rigid-ion model and exploiting an average t-matrix Greens function (ATM-GF) theory we appraised the vibrational properties of nitrogen and phosphorous doped Zn-Mn chalcogenides. Lattice relaxations around isolated NSe (PSe) defects in ZnSe and zb MnSe are evaluated by first principles bond-orbital model that helped construct perturbation models for simulating the localized vibrational modes (LVMs). Calculated shift of impurity modes for isotopic 14NSe (15NSe) defects in ZnSe offered a strong revelation of an inflexible defect-host interaction. By retaining force constant change parameter of 14NSe (15NSe) in heavily N-doped ZnSe, the ATM-GF theory predicted (a) three non-degenerate LVMs for the photoluminescence defect center VSe-Zn-14NSe (VSe-Zn-15NSe) of Cs symmetry, and (b) six impurity modes for the second nearest-neighbor NSe-Zn-NSe pair defect of C2v symmetry. From the range of simulated defect modes, we have ruled out the possibility of N-pairs and justified the presence of VSe-Zn-NSe complex centers - likely to be responsible for the observed large absorption bandwidth in highly N-doped ZnSe. High resolution measurements of FIR absorption and/or Raman scattering spectroscopy are needed to validate the accuracy of our theoretical conjectures.

ZnO-coated carbon nanotubes: inter-diffusion of carboxyl groups and enhanced photocurrent generation.

ZnO is a defect-governed oxide and emits light at both visible and UV regimes. This work employs atomic layer deposition to produce oxide particles on oxygenated carbon nanotubes, and the composites only show emission profiles at short wavelengths. The quenching of defect-related emissions at long wavelengths is verified, owing to carboxyl diffusion into oxygen vacancies, and doping is supported by ZnCO3 formation in oxide lattice. Fully coated tubes display an increased photocurrent and the quantum efficiency increases by 22 % relative to the bare nanotubes.

Carrier generation and recombination dynamics in type-II ZnSeTe/ZnMnSe quantum structures.

Type-II band alignment structure is coveted in the design of photovoltaic devices, since it is beneficial for the transport of photogenerated carriers. Here we study the generation and recombination dynamics of carriers in a type-II quantum structure composed of ZnSe0.92Te0.08 highly mismatched alloys (HMAs) and Zn0.97Mn0.03Se. The photoinduced holes at the ZnSe0.92Te0.08 HMAs firstly undergo rapid relaxation to the isoelectronic centers above the valence band edge and subsequently recombine with the free electrons in the Zn0.97Mn0.03Se. The long carrier lifetimes over 120 ns induced by spatially indirect excitons that are bound to isoelectronic Te trapping states further increase with increasing temperature.

Electronic properties of free-standing TiO2 nanotube arrays fabricated by electrochemical anodization.

Nanotubular TiO2 has attracted considerable attention owing to its unique functional properties, including high surface area and vectorial charge transport along the nanotube, making it a good photocatalytic material. Anodic TiO2-nanotube (TiNT) arrays on a Ti foil substrate were prepared by electrochemical anodic oxidation and SEM/HRTEM/XRD analyses have suggested that the walls of TiO2 tubes are formed from stacked [101] planes (anatase). Both HRTEM and XRD indicate an interplanar spacing of d101 = 0.36 nm in the wall structure. Despite the large amount of work done on nanotube synthesis, a thorough investigation of the electronic and atomic structures of free-standing TiNT arrays has not yet been carried out. X-ray absorption spectroscopy (XAS), resonant inelastic X-ray scattering (RIXS) and scanning photoelectron microscopy (SPEM) are employed herein to examine the electronic and atomic structures at the top and bottom of TiNT arrays. These analyses demonstrate the presence of mixed valence states of the Ti ions (Ti(3+) and Ti(4+)) and a structural distortion at the bottom cap region of the TiNT. Additionally, the results obtained herein suggest the formation of a defective anatase phase at the bottom cap barrier layer between the Ti foil substrate and TiNT during the growth of electrochemically anodized nanotubes.

Optical properties associated with strain relaxations in thick InGaN epitaxial films.

Structural and optical properties of thick InGaN layers with strain and composition inhomogeneities are investigated. High resolution x-ray diffractions (XRD) and reciprocal space mapping (RSM) along an asymmetric axis reveal that the In composition inhomogeneity is accompanied by strain relaxations during the growth of thick InGaN layers. According to the structural analysis, the commonly observed double photoluminescence (PL) peaks have been confirmed to be associated with the strain relaxation in thick InGaN films. Temperature-dependent PL measurements further indicate that the relaxed phase in InGaN films exhibits better emission efficiency than the strained phase. Recombination dynamics reveal that the carrier localization effect is more pronounced in the relaxed phase due to the compositional pulling effect. The correlations between emission efficiency and localization effect in thick InGaN films are discussed.

Local geometric and electronic structures of gasochromic VO(x) films.

VOx films were deposited by radio-frequency reactive magnetron sputtering from a vanadium target at room temperature. Local atomic and electronic structures of the films were then modified by thermal annealing. The oxidation state and structural and gasochromic properties of the films were elucidated by X-ray absorption spectroscopy. Analytical results indicate that the as-deposited VOx films were amorphous with mixed V(4+) and V(5+) valences. The amorphous VOx had a disordered and expanded lamellar structure resembling that of polymer-intercalated V2O5 gels. VOx films were crystallized into orthorhombic V2O5 at 300 °C, and the lamellar structure was eliminated at 400 °C. Additionally, the gasochromic reaction reduced the vanadium valence via intervalence transitions between V(5+) and V(3+). Moreover, removing the lamellar structure reduced the gasochromic rate, and the gasochromic reaction transformed the V2O5 crystalline phase irreversibly into an H1.43V2O5 phase. Based on the results of this study, amorphous VOx with a lamellar structure is recommended for use in H2 gas sensors.

Structural and surface characterizations of 2D ß-In2Se3/3D ß-Ga2O3 heterostructures grown on c-Sapphire substrates by molecular beam epitaxy.

Integrating two-dimensional (2D) layered materials with wide bandgap ß-Ga2O3 has unveiled impressive opportunities for exploring novel physics and device concepts. This study presents the epitaxial growth of 2D ß-In2Se3/3D ß-Ga2O3 heterostructures on c-Sapphire substrates by plasma-assisted molecular beam epitaxy. Firstly, we employed a temperature-dependent two-step growth process to deposit Ga2O3 and obtained a phase-pure ( 2 ¯ 01 ) ß-Ga2O3 film on c-Sapphire. Interestingly, the in-situ reflective high-energy electron diffraction (RHEED) patterns observed from this heterostructure revealed the in-plane 'b' lattice constant of ß-Ga2O3 ~ 3.038Å. In the next stage, for the first time, 2D In2Se3 layers were epitaxially realized on 3D ß-Ga2O3 under varying substrate temperatures (Tsub) and Se/In flux ratios (RVI/III). The deposited layers exhibited (00l) oriented ß-In2Se3 on ( 2 ¯ 01 ) ß-Ga2O3/c-Sapphire with the epitaxial relationship of [ 11 2 ¯ 0 ] ß-In2Se3 || [010] ß-Ga2O3 and [ 10 1 ¯ 0 ] ß-In2Se3 || [102] ß-Ga2O3 as observed from the RHEED patterns. Also, the in-plane 'a' lattice constant of ß-In2Se3 was determined to be ~ 4.027Å. The single-phase ß-In2Se3 layers with improved structural and surface quality were achieved at a Tsub ~ 280 °C and RVI/III ~ 18. The microstructural and detailed elemental analysis further confirmed the epitaxy of 2D layered ß-In2Se3 on 3D ß-Ga2O3, a consequence of the quasi-van der Waals epitaxy. Furthermore, the ß-Ga2O3 with an optical bandgap (Eg) of ~ 5.04 eV (deep ultraviolet) when integrated with 2D ß-In2Se3, Eg ~ 1.43eV (near infra-red) can reveal potential applications in the optoelectronic field.

Nanotribological Characteristics of the Al Content of AlxGa1-xN Epitaxial Films.

The nanotribological properties of aluminum gallium nitride (AlxGa1-xN) epitaxial films grown on low-temperature-grown GaN/AlN/Si substrates were investigated using a nanoscratch system. It was confirmed that the Al compositions played an important role, which was directly influencing the strength of the bonding forces and the shear resistance. It was verified that the measured friction coefficient (µ) values of the AlxGa1-xN films from the Al compositions (where x = 0.065, 0.085, and 0.137) were in the range of 0.8, 0.5, and 0.3, respectively, for Fn = 2000 µN and 0.12, 0.9, and 0.7, respectively, for Fn = 4000 µN. The values of µ were found to decrease with the increases in the Al compositions. We concluded that the Al composition played an important role in the reconstruction of the crystallites, which induced the transition phenomenon of brittleness to ductility in the AlxGa1-xN system.

Effects of Oxygen Pressure on the Microstructures and Nanomechanical Properties of Samarium-Doped BiFeO3 Thin Films.

In this study, samarium (Sm-10at%)-doped BiFeO3 (SmBFO) thin films were grown on platinum-coated glass substrates using pulsed laser deposition (PLD) to unveil the correlation between the microstructures and nanomechanical properties of the films. The PLD-derived SmBFO thin films were prepared under various oxygen partial pressures (PO2) of 10, 30, and 50 mTorr at a substrate temperature of 600 °C. The scanning electron microscopy analyses revealed a surface morphology consisting of densely packed grains, although the size distribution varied with the PO2. X-ray diffraction results indicate that all SmBFO thin films are textured and preferentially oriented along the (110) crystallographic orientation. The crystallite sizes of the obtained SmBFO thin films calculated from the Scherrer and (Williamson-Hall) equations increased from 20 (33) nm to 25 (52) nm with increasing PO2. In addition, the nanomechanical properties (the hardness and Young's modulus) of the SmBFO thin films were measured by using nanoindentation. The relationship between the hardness and crystalline size of SmBFO thin films appears to closely follow the Hall-Petch equation. In addition, the PO2 dependence of the film microstructure, the crystallite size, the hardness, and Young's modulus of SmBFO thin films are discussed.

Ferroelectricity and Oxide Reliability of Stacked Hafnium-Zirconium Oxide Devices.

In this work, we investigate the ferroelectricity of stacked zirconium oxide and hafnium oxide (stacked HfZrO) with different thickness ratios under metal gate stress and simultaneously evaluate the electrical reliability of stacked ferroelectric films. Based on experimental results, we find that the stacked HfZrO films not only exhibited excellent ferroelectricity but also demonstrated a high performance on reliability. The optimized condition of the 45% Zr proportion exhibited a robust ferroelectric polarization value of 32.57 µC/cm2, and a polarization current with a peak value of 159.98 µA. Besides this, the ferroelectric stacked HfZrO also demonstrated good reliability with a ten-year lifetime under >-2 V constant voltage stress. Therefore, the appropriate modulation of zirconium proportion in stacked HfZrO showed great promise for integrating in high-performance ferroelectric memory.

Self-Trapped, Thermally Equilibrated Delayed Fluorescence Enables Low-Reabsorption Luminescent Solar Concentrators Based on Gold-Doped Silver Nanoclusters.

Reabsorption-free luminescent solar concentrators (LSCs) are crucial ingredients for photovoltaic windows. Atomically precise metal nanoclusters (NCs) with large Stokes-shifted photoluminescence (PL) hold great promise for applications in LSCs. However, a fundamental understanding of the PL mechanism, particularly on the excited-state interaction and exciton kinetics, is still lacking. Herein, we studied the exciton-phonon coupling and singlet/triplet exciton dynamics for gold-doped silver NCs in a solid matrix. Following photoexcitation, the excitons can be self-trapped via strong exciton-phonon coupling. Subsequently, rapid thermal equilibration between the singlet and triplet states occurs due to the coexistence of small energy splitting and spin-orbit coupling. Finally, broadband delayed fluorescence with a large Stokes shift can be generated, namely, self-trapped, thermally equilibrated delayed fluorescence (ST-TEDF). Benefiting from superior ST-TEDF, we demonstrated efficient LSCs with minimized reabsorption.

Solid Phase Epitaxy of Single Phase Two-Dimensional Layered InSe Grown by MBE.

Single-phase two-dimensional (2D) indium monoselenide (γ-InSe) film is successfully grown via solid phase epitaxy in the molecular beam epitaxy (MBE) system. Having high electron mobility and high photoresponsivity, ultrathin 2D γ-InSe semiconductors are attractive for future field-effect transistor and optoelectronic devices. However, growing single-phase γ-InSe film is a challenge due to the polymorphic nature of indium selenide (γ-InSe, α-In2Se3, ß-In2Se3, γ-In2Se3, etc.). In this work, the 2D α-In2Se3 film was first grown on a sapphire substrate by MBE. Then, the high In/Se ratio sources were deposited on the α-In2Se3 surface, and an γ-InSe crystal emerged via solid-phase epitaxy. After 50 min of deposition, the initially 2D α-In2Se3 phase was also transformed into a 2D γ-InSe crystal. The phase transition from 2D α-In2Se3 to γ-InSe was confirmed by Raman, XRD, and TEM analysis. The structural ordering of 2D γ-InSe film was characterized by synchrotron-based grazing-incidence wide-angle X-ray scattering (GIWAXS).

The Effect of Heavy Fe-Doping on 3D Growth Mode and Fe Diffusion in GaN for High Power HEMT Application.

The high electron mobility transistor (HEMT) structures on Si (111) substrates were fabricated with heavily Fe-doped GaN buffer layers by metalorganic chemical vapor deposition (MOCVD). The heavy Fe concentrations employed for the purpose of highly insulating buffer resulted in Fe segregation and 3D island growth, which played the role of a nano-mask. The in situ reflectance measurements revealed a transition from 2D to 3D growth mode during the growth of a heavily Fe-doped GaN:Fe layer. The 3D growth mode of Fe nano-mask can effectively annihilate edge-type threading dislocations and improve transfer properties in the channel layer, and consequently decrease the vertical leakage current by one order of magnitude for the applied voltage of 1000 V. Moreover, the employment of GaN:C film on GaN:Fe buffer can further reduce the buffer leakage-current and effectively suppress Fe diffusion.

In Situ/Operando Soft X-ray Spectroscopic Identification of a Co4+ Intermediate in the Oxygen Evolution Reaction of Defective Co3O4 Nanosheets.

Defect engineering is an important means of improving the electrochemical performance of the Co3O4 electrocatalyst in the oxygen evolution reaction (OER). In this study, operando soft X-ray absorption spectroscopy (SXAS) is used to explore the electronic structure of Co3O4 under OER for the first time. The defect-rich Co3O4 (D-Co3O4) has a Co2.45+ state with Co2+ at both octahedral (Oh) and tetrahedral (Td) sites and Co3+ at Oh, whereas Co3O4 has Co2.6+ with Co2+ and Co3+ at Td and Oh sites, respectively. SXAS reveals that upon increasing the voltage, the Co2+ in D-Co3O4 is converted to low-spin Co3+, some of which is further converted to low-spin Co4+; most Co2+ in Co3O4 is converted to Co3+ but rarely to Co4+. When the voltage is switched off, Co4+ intermediates quickly disappear. These findings reveal Co(Oh) in D-Co3O4 can be rapidly converted to active low-spin Co4+ under operando conditions, which cannot be observed by ex situ XAS.

Effect of Ag-Decorated BiVO4 on Photoelectrochemical Water Splitting: An X-ray Absorption Spectroscopic Investigation.

Bismuth vanadate (BiVO4) has attracted substantial attention on account of its usefulness in producing hydrogen by photoelectrochemical (PEC) water splitting. The exploitation of BiVO4 for this purpose is yet limited by severe charge recombination in the bulk of BiVO4, which is caused by the short diffusion length of the photoexcited charge carriers and inefficient charge separation. Enormous effort has been made to improve the photocurrent density and solar-to-hydrogen conversion efficiency of BiVO4. This study demonstrates that modulating the composition of the electrode and the electronic configuration of BiVO4 by decoration with silver nanoparticles (Ag NPs) is effective in not only enhancing the charge carrier concentration but also suppressing charge recombination in the solar water splitting process. Decoration with a small number of Ag NPs significantly enhances the photocurrent density of BiVO4 to an extent that increases with the concentration of the Ag NPs. At 0.5% Ag NPs, the photocurrent density approaches 4.1 mA cm-2 at 1.23 V versus a reversible hydrogen electrode (RHE) under solar simulated light illumination; this value is much higher than the 2.3 mA cm-2 of pure BiVO4 under the same conditions. X-ray absorption spectroscopy (XAS) is utilized to investigate the electronic structure of pure BiVO4 and its modification by decoration with Ag NPs. Analytical results indicate that increased distortion of the VO4 tetrahedra alters the V 3d-O 2p hybridized states. Additionally, as the Ag concentration increases, the oxygen vacancy defects that act as recombination centers in BiVO4 are reduced. In situ XAS, which is conducted under dark and solar illumination conditions, reveals that the significantly enhanced PEC performance is attributable to the synergy of modulated atomic/electronic structures and the localized surface plasmon resonance effect of the Ag nanoparticles.

Pressure induced structural phase crossover of a GaSe epilayer grown under screw dislocation driven mode and its phase recovery.

Hydrostatically pressurized studies using diamond anvil cells on the structural phase transition of the free-standing screw-dislocation-driven (SDD) GaSe thin film synthesized by molecular beam epitaxy have been demonstrated via in-situ angle-dispersive synchrotron X-ray diffraction and Raman spectroscopy. The early pressure-driven hexagonal-to-rock salt transition at approximately ~ 20 GPa as well as the outstandingly structural-phase memory after depressurization in the SDD-GaSe film was recognized, attributed to the screw dislocation-assisted mechanism. Note that, the reversible pressure-induced structural transition was not evidenced from the GaSe bulk, which has a layer-by-layer stacking structure. In addition, a remarkable 1.7 times higher in bulk modulus of the SDD-GaSe film in comparison to bulk counterpart was observed, which was mainly contributed by its four times higher in the incompressibility along c-axis. This is well-correlated to the slower shifting slopes of out-of-plane phonon-vibration modes in the SDD-GaSe film, especially at low-pressure range (< 5 GPa). As a final point, we recommend that the intense density of screw dislocation cores in the SDD-GaSe lattice structure plays a crucial role in these novel phenomena.